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Timber size criteria

Started by scgargoyle, August 11, 2007, 04:53:18 PM

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scgargoyle

I'm playing with timber frame design, and I'm trying to figure out what really determines the size of a frame member- load bearing over a distance, or having enough material for the mortise and tenon? In other words- could a 6x6 be strong enough to span a certain distance, but not have enough material for a strong joint?  I am strongly considering Timberlinx (yes, I know, tain't a REAL timber frame), and it would seem to me that they should allow for a somewhat smaller beam, due to not having to remove so much wood at the joint. Why Timberlinx? 1) I'm too old, and don't have enough time to learn a new trade. 2) I think they are stronger, esp. more than a sloppy, amateur joint. 3) It's my house. I'm planning a 16 X 24 frame, 10' eaves, 12/12 pitch, with bents on 8' centers. All trusses would be king post, probably with struts. There is no 2nd floor to support. I think 8X8's all around should be plenty, esp. in the south with a very light snow load (10 psf) and fairly low wind load. I found out I'm going to have to have the timber frame portion of my house engineered anyhow, but I want to at least come close. Any thoughts?
I hope my ship comes in before the dock rots!

Dave Shepard

You are correct in that the timbers were often sized to accomodate the joinery. How much are the timberlinx per joint? You may be able to find an itinerent (sp) timber framer to cut the frame for an equal amount. I have heard some fairly high numbers for some of the metal connectors, but I don't know how closely the numbers compare.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

scgargoyle

I ran some numbers just to compare. Without struts, my frame would use 60 Timberlinx, which average about $40 each, depending on length, for a joinery cost of $2400. With struts, it goes up to $2880. I've only had one quote from an itinerant so far, at "$7500 to $9500". Either way, you still have the cost of materials, plus any heavy equipment (crane) for the raising. My real purpose behind all this is to cut  my own frame in my A/C garage, here in FL, then haul it to SC and raise it. I can buy locally milled cypress for $1.60 Bd/ft, which is cheaper than anywhere else I've been quoted for timbers. I would think cypress would make a nice frame, and relatively rot/insect resistant.
I hope my ship comes in before the dock rots!

logwalker

I too am considering the timberlinx system for constructing my next house. What are you using to miter the posts and beams? Would you need to buy their drilling jig?
Have you seen anybody else with an less expensive  alternative? What is your timeframe for the project? Joe
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

scgargoyle

I'm a toolmaker by trade, so I'll probably come up with something on my own to cut timbers. I was thinking about a cross between a chop saw and a chainsaw. Either that, or buy one of those big scary 16" Makita saws.The Timberlinx drilling jig is supposed to be pretty good, so I'll probably just buy their's, although I've thought of making one. I guess once you're done with your frame, you could probably sell the specialized tools to the next guy, or go in the business. :D Our time frame is about 2 years out, which is why I'm doing a lot of research now. Ultimate plans are for a central 16X24 great room, with stick-built wings on either side. I'd like to extend the timber frame one bent forward for a front porch, and 2 bents rearward for a dramatic timber frame back porch overlooking the mountains. Budget constraints may eliminate some or all of the timber frame- we'll just have to see what the real estate market in FL is like when we go to sell. Our land is ideal for a walk-out basement. Total square footage is only about 1300, but the basement will double that, if I like. This will be a semi-retirement home, so everything has to be on one level for when we get old(er). I've seen one alternative (Stavebolt?) but it is much more expensive, and not as useful. There are also steel sockets out there, which I may use for my barn, but I don't like the look of them for the house- too industrial. Lumberlinks, I think they're called.
I hope my ship comes in before the dock rots!

Dave Shepard

Watch out for those 16" saws, they are hungry, and they like red meat. ;) I had always wondered what running a hand held buzz saw was like, now I know.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Don P

 :D :D, I call it a hand held sawmill.
Really its fairly tame/ underpowered. It has the same motor as the 7-1/4" saw with an additional reduction to keep the tip speed under control and give more torque. The Makita 16" is limited to about 6-1/4" depth of cut.

I've seen a chainsaw chopbox, kinda rugged cut but accurate. Another company used a 24" circular blade on a homemade chopbox, I'd lean that way if making a tool. Another neat one was a 16" on linear bearings over a roller table, it worked like a sawbuck.

Don't forget Simpson or engineered buried knifeplates or...

A toolmaker can probably fabricate his own connectors  ???

scgargoyle

I thought about making connectors, but it would add a lot of time to the project, and I wouldn't have any engineering to hand to the inspector.
I hope my ship comes in before the dock rots!

Don P

Connections should be engineered, I have had them fabricated locally. Where to spend time is always a judgement call though  :)

TexasTimbers

I am a Timberlinx apologist. I may never become highly proficient in cutting joints because of it but oh well . . .

I do of course want to, and will,  use some handcut joints but the biggest part of our add-on will be Timberlinx. Much quicker. Less expensive. Tons less labor. Stronger. What's not to like.
The oil is all in Texas, but the dipsticks are in D.C.

Don P

I can't remember if I've posted this list before, there's alot of glulam post and beam type technical info there. The "Glulam Connection Details" might be worth reading. Alot of the thinking in that guide is applicable to any work with heavy timber. You'll need to register to download their pdf's, their site has alot of good info.
http://www.apawood.org/level_c.cfm?content=pub_glu_libmain

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